Filter devices of this type are readily available on the market in a plurality of designs and versions. They are used, among other purposes, to filter dirt in fluids, such as hydraulic oil, out of these fluids. Hydraulic oil is fouled during installation and when the respective hydraulic system is started up. In addition to this initial fouling, fouling during operation can occur, for example, by penetration of dirt at the hydraulic tank due to inadequate tank ventilation, pipe penetrations, piston rod seals, and the like. To the extent fouling within the fluid stored in the hydraulic tank occurs in hydraulic systems of machines such as earth moving machines, excavators or the like, it can be advantageous to implement filtration directly in the region of the hydraulic tank, for example, by installing the filter device directly in the tank. The hydraulic oil is removed from the tank contents being delivered to filter out dirt directly to a filter element held in the filter housing. The fluid which has been cleaned in this way then returns again to the tank contents via the filter housing. In these solutions, the filter device cleans only the contents of the tank. Solutions are also conceivable in which the filter device delivers the correspondingly filtered and cleaned fluid to the hydraulic circuit of the machine, then returning to the tank the fluid fouled with solid particles in the circulation in the hydraulic circuit.
In the solutions in which the filter device filters only the contents of the tank by fluid being removed from the tank filtered and then returned again to the tank contents, it can be advantageous, when the filter element has to be changed to block off the contents of the fluid means, especially in the form of a hydraulic tank, relative to the filter housing. In this process, the filter housing with the used filter element can be completely dismounted from the fluid means, specifically the tank, and replaced by a filter housing with a fresh filter element without the need to interrupt operation of the respective hydraulic system.
In the known solutions, tedious and time-consuming measures must be carried out in conjunction with changing the filter housing. Thus, the pipes which belong to the connection system must be separated from one another and sealed tight in a complicated process. There is also the danger that larger amounts of fluid will escape from the filter housing and/or fluid means as a type of leaking oil flow when the filter housing is being dismounted. This leaking leads to environmental pollution problems. Moreover, the actuation of the fastening means by the operator when removing and re-attaching the filter device to the fluid means must be done carefully to ensure trouble-free operation of the fluid system.